Knack - A perfect launch exclusive to show the fun options and graphics the PS4 has to offer.
Forgive my soapbox for a moment, but I have to agree that Knack was a very, very fun platformer that showed off the Pixar-esque graphics the PS4 is capable of. I had a blast playing this game and find it atrocious how reviewers tore it apart while giving something like Mario (insert whatever title follow-up here) 4001 a free pass.
The negative reviews were because it was a launch title, same with Killzone. Reviewers expect way too much from launch lineups.
Reviewers expect launch titles to justify the purchase of a new system by themselves, which is silly. The way I always look at buying a system at launch is "are there enough games I'll want to play coming for it before it's likely to see a significant price drop?" If so, there's no point in waiting IMO. And there definitely were enough for the PS4.
Typically, I follow your same train of thought about how many good games will be out before a price drop. I pretty much buy PlayStation consoles at or close to launch regardless. They always end up with a ton of great games, many exclusives published by Sony themselves.
The situation with Knack always bugged me. It was never pitched as a genre-changing game. It was a fun, challenging platformer with gorgeous Pixar-like graphics, fun characters and an interesting mechanic where you collected relics and grew in size. When you reached maximum size, you could just wreck everyone and everything. The only criticism I can personally level against the game was the fixed camera, just because we've become accustomed to being able to manipulate the camera in most 3D games now.
Killzone Shadow Fall is another launch title that caught a lot of flak and I thought was great. I've replayed that game several times and loved it each time. Was it perfect? No. But being a launch title made in a relatively short timespan, Guerilla Games did a bang-up job on it.